Born in Motherwell,[3] Devlin grew up in a street near to fellow footballer Mark Reynolds and attended the same school, where the older pupil was held up as an example to follow.

[4] As a teenager Devlin spent time in the youth systems of Heart of Midlothian, Aberdeen and Celtic,[4] making the squad for a Glasgow Cup final with the latter in May 2010.

[15] In the last regular game of the 2016–17 season, Devlin suffered a serious knee injury, meaning he missed the club's two relegation play-off matches.

[17][6] He eventually made his competitive debut for Aberdeen on 26 July 2018, in the first leg of a Europa League tie against Burnley at Pittodrie Stadium.

[18][19] In August 2020 he was one of eight Aberdeen players who received a suspended three-match ban from the Scottish FA after they breached coronavirus-related restrictions by visiting a bar earlier in the month.